Cutting lubricant



Patented Jan. 23, 1940 PATENTf-oFFicE CUTTING LUBRICANT Waldo L. Steiner, Ponca City, kla., assignor to Continental Oil Company, Ponca corporation of Delaware City, Okla., a

No Drawing. Application February 3; 1936, Serial No. 62,170

11 Claims.

My invention relates to a cutting lubricant for use in the lubrication of the cutting tools in machines designed for cutting and threading metallic pipes, rods, bolts, and the like.

Heretofore, cutting lubricants consisted mainly of blends of lubricating oil and a chemical combination of sulphur, usually, with a fatty compound. These early types of cutting oils are fairly satisfactory for most uses but nevertheless have certain distinct disadvantages. Most of them have an objectionable odor and are very dark in color and some are very inefficient. Usually they are rather expensive and difficult to prepare. A greatnumber have an irritating effect on the skin of the operator. Some are extremely viscous when cold and are therefore very unsatisfactory on cold mornings in many shops which are not well heated. Some of the newer cuttings lubricants contain sulphur 20 compounds other than those derived from fatty acid derivatives. In all of the above compounds; howeven'the sulphur is in chemical combination. Furthermore, other things being equal, the emciency of this type of cutting oil is largely dependent on the instability of the sulphur-compound. The more stable thecompound the less eflicient it is as an aid in cutitng and relatively more of it will have to be used for a satisfactory cutting lubricant. On the other hand, if the compound is very unstable, the cutting oil made from it will likely deteriorate in storage.

The object of my invention is to provide an improved cutting lubricant. I have discovered that an improved and superior cutting lubricant 35 may be prepared by blending a petroleum lubricant with a true physical solution of sulphur in certain suitable solvents. My investigation of this new type of cutting lubricant gives sufficient evidence to prove that it is superior to the con- 4 ventional chemically combined sulphur cutting lubricant in several ways. In the first place, much less sulphur is required to obtain the same efliciency for thelubricant. Secondly, it makes it possible toprepare a cutting lubricant very light in color and quite odorless and one which does notirritate the skin in the slightest degree. Also, they do not congeal at low temperatures. While some old type lubricants containing chemically combined sulphur may be obtained odorless they are invariably dark in "color and are usually rather viscous around 30 F.

There are many solvents for sulphur, one of the best being carbon bisulphides. This solvent could not be used commercially in a cutting lubricant because of its high volatility and inflammability. There are other solvents for sulphur to which these objections would not apply which, for other reasons, such as obnoxious odor and insolubility in petroleum oil, I do not prefer. Phenol and aniline are examples. The greatest difficulty in finding a suitable solvent for sulphur for a cutting oil is to discover one which will not allow sulphur to separate out when the mixture is stored at relatively low temperatures. Naturally, a marketable cutting lubricant must be stable under all kinds of possible storage conditions such as might be encountered in winter. I

I have found that solutions of sulphur in certain derivatives of naphthalene and similar high boiling aromatic compounds when added to a petroleum lubricant, do not precipitate out sulphur even at very low temperatures when the amount of sulphur is kept within certain limits. and these form the preferred solutions for use in my invention. Naphthalene itself is odoriferous and not very soluble in petroleum oils at low temperatures and, therefore, is not preferred. It is, however, a very efficient solvent for sulphur, especially at high temperatures. Considerable investigation was therefore given to the naphthalene derivatives which are soluble in petroleum at low temperatures. This work led to the discovery that, among the better sulphur solvents which are soluble in petroleum at lowtemperatures are the chlorinated derivatives of naphthalene. Furthermore, the best suited of the chlo-v rine derivatives are the pentaand hexa-chloroa two compounds were;

naphthalenes. -These found to be able to dissolve more sulphur for a given weight when mixed with a petroleum lubri-' cant than any other solvent investigated, either at high or low temperatures. They have the added desirable properties of being entirely odorless, practically colorless, and quite non-toxic. These two compounds, holding sulphur in solution and-dissolved in -a petroleum lubricant, will not precipitate out sulphur when stored for several weeks at 0 F. if thesulphur content does not exceed 12 percent by'weight of the chloronaphthalene in the mixture. These chloronaphthalenes are themselves soluble in a petroleum lubricant to the extent of about percent at 0 F.

They are more soluble in the heavier lubricants such as oils having an S. S. U. viscosity of about 250 at 100 F. than in lighter oils having a viscosity of '70 to 100 at 100 F. Thus it is possible to make a cutting lubricant stable to the most adverse storage conditions from these two chloronaphthalenes, containing 1.2 percent of physically dissolved sulphur. Since sulphur in a physically dissolved state is many times more efilcient in a cutting lubricant than when it is 'in the combined state, this is sufiicient to give an excellent and superior cutting lubricant.

Other solvents among the naphthalene derivatives which are satisfactory, but not as eflicient as the above two, are as follows in the descending order of their suitability for use in this inven tion: heptaand higher chlorine derivatives of naphthalene; mono-, di-, tri-, and tetra-chloro derivatives; decahydronaphthalene (decalin); alkylated naphthalenes (methyl and ethyl); coal tar oil out boiling between 400 F. and 600 F.

and higher (large a mixture of alkyl derivatives.

and other hydrogen- In preparing a cutting lubricant according to my invention, the following procedure is recommended. The petroleum lubricant is first mixed with the sulphur solvent in the proportion that it is calculated necessary for the amount of sulphur to be held in solution. The mixture is heated to slightly above the melting point of 5111- phur (or about 250 F.) and the sulphur is then stirred in until all dissolves. No chemical reaction takes place betweensulphur and lubricating oilor naphthalene derivatives at this temperature and the solution is purely physical.

Only a few minutes are required-for the solution to take place. Some specific examples of different mixtures of this new type of cutting lubricant with tests to show their value are given, by

' way of illustration only, and not by way of limitation. The sulfur may also be first dissolved in the sulfur solvent and then (in solution) added to the lubricating oil. I

Example No. 1.A mixture of parts by weight of light lubricating oil and 20 parts by weight of mono-chloro-naphthalene was heated to 250 F. and one part of sulphur was stirred in until it dissolves. A sample of this mixture stored at 0-F. for several days did not precipitate sulphur. Tested in a 2" thread cutting machine it gave excellent results. The threads were extremely smooth. Its color was very light and its transparency was an aid to the operator in obtaining the best results, thus avoidinga drawback.

of the dark sulphuretted cutting oil containing chemically combined sulphur. On very cold 'mornings no trouble was encountered from difllculty to flow. A comparison was made between the results obtained with this lubricant and a highly recommended cutting 011 containing chemically combined sulphur lubricant had a larger amount of sulphur than the lubricant of my invention. The test pipe threaded was a piece of very hard, used-oilewell casing. A number of threads cut with the sulphur-combined lubricant were compared with a number of threads cut with the new type lubricant. The latter threads were appreciably smoother and showed less tearing than the former, thus demonstrating the improved efliciency of a physical solution of sulphur as a cutting lubricant.

Example No. 2.-A mixture of 80 parts by weight of a light petroleum lubricant and 20 parts by weight of coal tar oil (B. P. range 400 F. to 580 F.) was heated to 250 F. and one part by weight of sulphur stirred in until it entirely dissolved. This cutting lubricant was used in a 2" thread cutting machine for two months high class extreme pressure with consistently superior results with respect to the threads obtained while using it.

Example No. 3.--A mixture of parts by weight of petroleum lubricant and 15 "parts by weight of decalin was heated to 250 F. and one sulphur. It was very light. and transparent,

having a 2 color (A. S. T. M.) and was entirely free of any odor. The cold test was not raised by the addition of the sulphur and chloronaphthalene. When tested on a thread cutting machine it gave results which were superior to any obtained from any cutting lubricant ever tested on this machine.

Considerably less sulphur in the blend than was used in the above examples is sufficient to give a good cutting lubricant. Even as little as .2 percent sulphur in the blends of my invention gives satisfactory results. Generally, the sulphur content of this type of cutting lubricant should' lie between .1 percent and 2 percent. More will not be necessary and less will not be entirely satisfactory.. The quantity of sulphur to be used is determined by the use to which the cutting oil will be put.

. The addition of 1 percent or 2 percent of oleic acid to this type of cutting lubricant seems to have a slightly beneficial effect but is not necessary.

This new type of cutting lubricant may be blended with the old sulphur, chemical compound type cutting lubricant to improve the latter.

The petroleum lubricants used in the preparation of these cutting oils may be of naphthenic, paraffinic or mixed base source. They may be either raw or refined and should be selected so that the finished lubricant will have a viscosity of to 300 seconds at 100 F. (S. S. U.). Naturally, cutting lubricants with viscosities outside this range may be useful but as a rule are not as satisfactory as those within this range.

Although a cutting lubricant is the primary object of. this invention, it is possible to obtain a gear lubricant by merely substituting a more viscous hydrocarbon lubricant for the relatively low viscosity oil used in preparing cutting lubricants in the foregoing compositions.

Having thus described my invention, what I claim is:

1. A cutting lubricant comprising in combination a lubricating composition intimately ads mixed with a. solution of uncombined sulphur in a non-volatile, oil-soluble naphthalenic compound, the sulphur being present in an amount by weight from .1 of one percent to 2 percent.

2. A cutting lubricant comprising in combina-' tion 'a lubricating composition intimately admixed with a solution of uncombined sulphur in a non-volatile, oil-soluble aromatic. compound, the sulphur being present in an amount by weight from .1 of one percent to 2 percent.

3. A cutting lubricant comprising in combination a major proportion of a lubricant intimately admixed with a minor proportion of a physical solution of elemental sulphur in a naphthalenic solution of elemental sulphur in an aromatic compound, the solution being non-volatile and soluble inthe lubricant.

5. A composition of matter comprising in combination a major proportion of a lubricant and a, minor proportion of a physical solution of elemental sulphur, said solution being soluble in the lubricant and substantially non-volatile.

6. A composition of matter comprising a lubricant containing dissolved therein a physical solution of elemental sulphur, sulphur being present in the composition of matter in an amount between .1 of one percent and 2 percent by weight.

7. A lubricant comprising in combination a major proportion of said lubricant and a minor proportion of a solvent having dissolved therein uncombined elemental sulphur.

8. A cutting oil composition comprising in combination a major proportion of a lubricating oil and a minor proportion of a solution or elemental sulphur in a. substantially non-volatile halogenated aromatic compound, which is a mutual solvent for sulphur and mineral oil.

9. A cutting oil composition comprising in combination amajor proportion of a lubricating oil and a minor proportion of a solution of elemental sulphur in a substantially non-volatile halogenated derivative of naphthalene, which is a mutual solvent for sulphur and-mineral oil.

10. A cutting oil composition comprising in combination a. major proportion of a lubricating oil and a minor proportion of a solution of elemental sulphur in a substantially non-volatile chlorinated naphthalene compound, which is a mutual solvent for sulphur and mineral oil.

11. A cutting oil composition comprising in combination a major proportion of a lubricating oil and a minor proportion of a solution of elemental sulphur in a substantially non-volatile halogenated aromatic compound, which is a mutual solvent for sulphur and mineral oil, said elemental sulphur content not exceeding twelve percent by weight of the halogenated aromatic compound.

' WALDO L. S'I'EINER. 

